724Zman 0 #1 Posted August 7, 2012 I have a Wheel Horse 724Z Zero Turn 60" mower with a P224 Onan on it. Just recently it started stumbling and backfiring out the muffler only when the mower is engaged. I am not sure if it is starving for fuel but that was my first thought. I replaced the fuel pump, fuel filter and cleaned the carburetor. No improvement. With the mower deck off, it seems to have full power. Anybody have any ideas? Share this post Link to post Share on other sites
Jake Kuhn 1,579 #2 Posted August 7, 2012 well this might not be it but the onan on my d always backfired really bad and it turned out being a loose spark plug.~ Jake Share this post Link to post Share on other sites
JackC 617 #3 Posted August 7, 2012 If it runs fine and then all of sudden does not, the first thing I do is clean and reset the carburetor. My D-160 was backfiring. It was the carburetor. I soaked it overnight in carburetor cleaner and replaced the float valve and seat and the main jet. Huge difference in the way it starts and runs now, like night and day. It runs like a top and the backfiring is gone. My original carburetor settings were way off and way too rich but it did start and run. Did you follow the service manual procedure to reset the carburetor adjustments? Some recommend de-carboning and adjusting the valves and timing. Bruce says weak spark or spark plugs is usually the cause. Check all connections for corrosion including both ends of both plug wires. http://www.perr.com/phpBB3/viewtopic.php?f=14&t=4348 Share this post Link to post Share on other sites
TheReDStAnG 4 #4 Posted August 7, 2012 What do the spark plugs look like? If it backfiring through the exhaust I would have to say chances are your getting enough fuel (quite possibly too much). Verify consistent spark with timing light/spark tester with engine under load. My hunch is plugs/plug gap/wires. Share this post Link to post Share on other sites
TT-(Moderator) 1,162 #5 Posted August 8, 2012 Just recently it started stumbling and backfiring out the muffler only when the mower is engaged Another thing worth investigating would be the safety interlocks. (seat & PTO switches) One of them might be going bad, causing a voltage drop or intermittent loss of power at the ignition coil. Share this post Link to post Share on other sites
dbartlett1958 99 #6 Posted August 10, 2012 What TT said! I had this issue on my 416-H when turning because I was leaning in the seat, causing the seat switch to interupt the circuit. The problem initially had me thinking carb trouble, but it was just the seat switch. Runs great now. Share this post Link to post Share on other sites
